A Minnesota court was asked Friday to overturn the state’s controversial decision to allow a taconite mine to proceed on a major expansion without an environmental review.

The Minnesota Center for Environmental Advocacy (MCEA) said the Department of Natural Resource’s decision last month to let Minntac expand its open pit mine by 483 acres will add pollution to an operation that is already violating water quality laws by releasing too much sulfate and other pollutants into nearby lakes.

“We are asking them to find solutions to the current problems before they expand the mine,” said Kathryn Hoffman, an attorney with MCEA.

DNR officials decided in April that an environmental-impact statement — a $1 million to $3 million review of likely impacts on land, air and water — wasn’t needed for the expansion, which will extend the life of the mine by 16 years. Officials said the environment would be protected by the plant’s current water quality permit and a new permit likely to be granted soon. They also said other agencies, including the Minnesota Pollution Control Agency and the U.S. Army Corps of Engineers, provide additional oversight that protect the environment.

Minntac, which is owned by Pittsburgh-based U.S. Steel, employs some 1,400 workers and is one of the state’s largest taconite operations.

MCEA asked the Minnesota Court of Appeals to review the agency’s decision, arguing that the mine’s current permit fails to protect the water. Hoffman said the permit, which was granted in 1987 and continually extended since it expired in 1992, does not hold the company to water quality laws, or require it to use cleanup technology and systems that are now available.

DNR officials declined to comment on the appeal Friday, but said last month that they viewed the agency’s decision about the expansion as separate from the water quality permit. Officials for U.S. Steel declined to comment on the appeal.

Hoffman said Minntac’s existing 8,000-acre mine waste pit near Mountain Iron, Minn., is polluting nearby water with sulfate concentrations that are up to 60 times higher than the state’s limit. Sulfate has been linked to mercury contamination in fish, and can be toxic to wild rice. Hoffman said the waste pit is also discharging other pollutants, including chloride and manganese, which are not addressed in its permit.

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